Fluid-pressure brake system



Aug. 14. 1928.

F. s. DUESENB ER G FLUID PRESSURE BRAKE SYSTEM 5 Sheets-Sheet bi, R m

Inventor.-

Filed April 1, 1924 Aug. 14. I928.

F-. S. DUESENBERG FLUID PRESSURE BRAKE SYSTEM 5 Sheets-Sheen Filed April1, 1924 wgnvnir:

Aug. 14, 1928. 1,681,030

F. S. DUESENBERG FLUID PRESSURE BRAKE SYSTEM Filed April 1, 1924 5Sheets-Shem 5 \o o n o) c 3 lnvewior: Frgderflie Sflu7/sen6ewg, by I MW! tiys.

Aug. 14. 1928.

F. S. DU ESENBERG FLUID PRESSURE BRAKE SYSTEM Filed April 1924 5Sheets-$heet I nveuior izireiewigicfflzwfiewe y W W :9

Aug. 14. 1928.

F. S. DUESENBERG FLUID PRESSURE BRAKE SYSTEM Filed April 1924 5Sheets-$heet 5 f my QII R In ve niov F'redewicfflzgfeseu6er 'QW'it/71198.

' 45 of Fig. 2;

Patented A... 14,1928. I y 1,681,030

UNITED STATES PATENT OFFICE.

FREDERICK S. DUESENBERG, OF INDIANAPOLIS, INDIANA, ASSIGNOR T INDIAN-APOLIS CORPORATION, 01" WILMINGTON, DELAWARE, A CORPQRATION OF DELA-WARE.

FLUID-PRESSURE BRAKE SYSTEM,

Application filed April 1, 1924. Serial No. 703,421.

This invention relates to a novel and imbodiment of the invention whichis selected proved fluid pressure brake system having forexemplification, there is shown in Figs.

special utility in connection with steerable 1 and 2 a portion of thechassis of a motor vehicles, such as motor cars, and particuvehicle,minus apart of the motor and a part larly those whose front or steeringwheels, of the steering gear. The chassis has a pair 55 as well as therear or driving wheels are of front steering wheels 16 and a pair ofequipped with brakes. rear driving wheels 17, conventionally repre- Theinvention will be best understood by sent-ed in Fig. 2, front and rearaxles 18 and reference to the following description, when 19, frontandrear springs 20 and 21, and a taken in connection with theaccompanying spring-supported frame, the latter herein 60 drawings ofone illustrative embodiment comprising a pair of side members 22conthereof, while its scope will be more particunected by cross members23, 24, 25 and 26. larlypointed out in the appended claims. Herein, atorque tube 27, secured to the rear In the drawings: axle housing, ispivotally connected at its Fig. 1 is a plan of-a motor car chassis,front end to the'cross member 24. A motor, .65 equipped with a brakesystem exemplifying a portion of which'is shown ,at 28, is sliptheinvention; ported on theside members 22, and supports Fig. 2 is a sideelevation of the same; zfcluteh'and transmission having a housing Fig. 3is aside elevation, partly in verti- 29. The parts thus far describedmay beiof cal section, on an enlarged scale ,'-illustrating any usual orsuitable construction.- the master cylinder, brake-pedal and asso- Apart of the steering mechanism will now ciated parts; be described,reference being had at first to Fig. 3 is a sectional view on" anenlarged Fig.1. -Each of the front wheels may be scale on line 3 -3 ofFig. 3; provided with a usual hub 30, mounted to 25 -Fig. 4 is anelevation, partly in vertical turn on a stub axle or spindle 31' (seeFig. section, of the parts shown in Fig. 3; 13), herein formed as a partof, a'steering Fig. 5 is asectional view on line 55 of knuckle 32,. thelatter beingsuitably pivoted Fig. 4; v on the axle 18, as by theprovision of a pivot Fig. 6 is a sectional View on line 6-6 of. 33,herein secured. to the axle by a pin 34:. i 30 Fig. 5; The steeringknuckle herein is provided with Fig. 7 is a sectional view on line 7-7of upper and lower bearings 35 and 36, and has Fig." 5;intermediatethese bearings a recess 37, which Fi 8 is a sectional view011 line 88 of receives a boss 38 formed on the end of the Fig.% axle18. In'the present example, this boss 35 Fig. 9 is a sectional view online 9-9 of rests upon an anti-friction thrust bearing 39,

Fig. 3; e which contributes to the ease of steering of Fig. 10 is asectional view on line 10- 10 the vehicle. of Fig.9; Suitably secured tothe wheel hub 1s a Fig. 11 is a sectional view on line 11-11 brake-drum40, and enclosed by the latter is 40 of Fig. 9; v e a brake-shoe orshoes, herein exemplifiedby Fig. 12 is a detail longitudinal section, apair of brake-shoes 11 (see Fig. 15), hav-,., illustrating the strainerfor the liquid at the ing terminals 42. These shoesare preferbottom ofthe reservoir; ably provided with usual brake linings 43. Fig. 13 is asectional view on line 1313 The brake shoes are mounted on pivots 44,

. I carried by a. carrier 45, which turns in unison Fig. 14 is asectional view on an enlarged with the steering knuckle. I scale on line14-14 of Fig. 3; and The brake-shoe actuating mechanism will Fig. 15 isa sectional view on an enlarged now be described, reference being had toscale on line 15-15 of Fig. 13. the upper portionv of Fig. 15. A lever46 50 Referring to the drawings, and to the emis .fulcrumed at 47 on afloating support,'

such asthe lever 48, mounted on a pivot comprising a stud 49 on thesteering knuckle 32 The lever 46 is connected to the ternnnals of thebrake-shoes -11 by links 50 and 51, at opposite sides, respectively, ofthe fulcrum 47. about which the lever rocks in operating thebrake-shoes. It follows that rocking movement of the lever isaccompanied by movement of the brake-shoes in opposite directions.respectively. The brake-shoes are normally held in their retractedpositions by one or more springsv 5'2, directly connecting the terminals42 to which they are hooked. This spring resists applying movement ofthe. brake mccha nlsm. and restores the latter to its initial positionwhen the applying force is removed.

The applying force herein is furnished by a plunger, such as a pistonmounted to slide in a guide, herein a cylinder 51. The other end of thelever 16 simply rests upon the piston. \Vhen, therefore. the plunger israised, the lever is rocked on its fulcrum, and the brake-shoes arebrought into contact with the internal surface of the brake-drum. Therear wheel brakes are preferably generally similar to the front wheelbrakes hcrcinbefore described. and it is therefore deemed unnecessary todescribe them in detail, except to say that each of the rear wheels isprovided wit-h a hub (seeFig. 1), to which is suitably secured abrake-drum 56,-the brake-shoes in this case being actuated by cylinders57, like unto the cylinders 54 employed for the front wheel brakes.These cylinders are appropriately mounted on thcerear axle housing 19.

The invention contemplates the use of a. suitable fluid, such as oil orglycerine, for the operation of all four brakes, under the control of asingle actuating member conveniently located for operation by thedriver. In the present example, the actuating member is a pedal 58 (seeFig. 2), fulcrumed on a pivot 59, which in practice is the clutch shaft;Referring now to Fig. 3, this pedal is suitably connected with a fluidmotor, hereincomprising a master piston 60 (see Fig. 5) working ina'master cylinder 61. The piston and cylinder are pivotally mounted toswing to and fro, accompanying reciprocation of the piston in thecylinder, the latter to this end being provided with a downwardextension 62, which, as best shown in Fig. 14, presents axially alignedbosses constituting pivots 63 and 64,- which are mounted to turn inbearings 65 and 66 presented by two supporting brackets 67 and 68.Referring now to Fig. 4, the bracket 68 herein is appropriately securedto the transmission and clutch housing 29, as by a bolt-69 extendingthrough a lug 70 at the top of the bracket, while the bottom of thelatter presents two laterally extending lugs 71 (see Figs. 3 and 6),which may be secured to said housing by cap-screws or studs 72. Thebrackets are. held in definitely spaced relationship at their upper endsby a spacing sleeve T (see Fig. 1), which is interposed between thebrackets, and encircles a bolt 7-1, which extends through the brackets.Referring again to Fig. 14, the lower ends of the brackets aredefinitely spaced by shoulders 75 and 76, presented by the bosses (33and 64, respectively. A washer 77, secured to the boss 63 by a cap-screw78, holds the bracket 67 in proper relationship with the shoulder 75,while a washer 79, secured to the boss 64 by a stud 80, serves tomaintain the proper relationship between the bracket 68 and the shoulder76. Referring now to the upper left-hand portion of Fig. 3, the brackets67 and 68 are secured as by bolts 81 to a bracket 82, which presents abearing for the pivot 55) of the brake pedal, and is bolted to theclutch housing.

The piston herein is provided with a piston rod 83 (see Fig. 5), guidedby :1 cylindcrhead 84 secured to the upper end of the master cylinder.The upper end of the piston rod is pivotally connected to a lever,designated generally by the numeral 85. best shown in Fig. 10, which inturn is connected by a link 86 to the pedal 58. Relative adjustment ofthese parts herein is coliveniently accomplished by making the lever intwo parts 87 and 88, both fulcrmned on the sleeve 73, and adjustablyconnected to each other, as by a stud 85) carried by one of said parts,and extending through a segmental slot provided in the other. Aset-screw 91, threaded into a lug 9; on one part of the lever, restsagainst the other part of thelever, and affords a means of adjustment,while the stud 89 serves to clamp the two parts in the desired positionof adjustment. This adjustment enables one to predetermine the timing ofthe operation of the master piston with respect to related parts, suchas the pedal and the pressure booster presently to be described.

The lever 85, piston rod 83, piston 60 and cylinder 61, constitute ineffect a toggle, which straightens as the piston descends in thecylinder, and the relative arrangement of the parts is such as to causea relatively rapid expulsion of the fluid at the commencement of thedownward movement of the piston, and a decreasing speed of expulsionlater, as the piston continues to descend. The result is that when thebrake pedal is depressed, at first the brakes will move rapidly but withcomparatively little power, but as the movement progresses, the brakeswill be appliedwithincreasing force. A

suitable spring 93, herein attached at one end to the pedal (see theupper portion of Fig. 3) and at its other end to an appropriate fixedsupport 94; constantly tends to re-. store the pedal andconnectedpartsto the initial position represented in Fig. 3. The

adjustment of the lever 85 should be such that the toggle lacks aboutone-quarter of. an inch of reaching a straight-line position when thepedal is fully depressed.

It is important that the system be kept entirely filled with the liquid,otherwise its effectiveness would become impaired by the presence ofair, which is compressible, and I have therefore provided replenishingmeans new to be described, reference being had at first to Figs. 3 and4. A reservoir 95 adapted to contain a supply of liquid, is suitablysupported, as by securing the same to the master cylinder, herein bycap-screws or studs 96, and the reservoir is further supported byproviding the same with a downwardly extending arm 97, which, as shownin Fig. 14, has a bearing 98 on the boss 63, thelatter being providedwith a shoulder 99 serving as an abutment to limit inward movement ofthe bearing along the boss. It should here be-observed that the mastercylinder and reservoir are spaced apart (see Fig. 9), and that a portionof the bracket 67 extends between them. The reservoir is provided with asuitable filling cover 100.

Advantage is taken of the movements of the brake pedal to cause oil tobe supplied from the reservoir to the master cylinder, in case of lossthrough any cause, and to boost the pressure in the master cylindershould occasion arise for abnormally high pressure. To this end, I have,provided a pump comprising a cylinder 101 (see Fig. 5) having a piston102 working therein, the latter having a depending rod-103, which isactuated by though disconnected fI'OIIl the brake pedal. The lower endof Qthis piston rod is adapted for cooperation-' with a lever 104,fulcrumed on a pivot 105 carried by the master cylinder 61 about itspivotal axis, said lever being connected to the pedal bymechanism now tobe described, reference being had to Fig. 3. The connection is in thenature of a link, designated generally by the numeral 106, which ispivoted at its upper end to an arm 107, carried by the brake pedal,while the lower end of the link has a lost motion connection with thelever, as b providing the latter with a slot 108, whic receives a pin109 carried by the link. A suitably arranged sprin 110, best shown inFigs. 5 and 6, constant y tends to maintain the pin 109 at the u per endof the slot 108.

The purpose of this 0st motion connection is to permit the booster to beoperated by the lever 104 by hand, independently of the brake pedal,this being advantageous when initially filling the system with liquid.

Herein, the lever 104 presents a shank 111 for the convenient attachmentof an operating tube or rod for'use as a handle when 112 for vengagement with the lower end of the booster piston rod 103,;thisabutment in the present example being conveniently formedas a bolt,extending through the lever and secured thereto by a nut/113. In thenormal position of the brake pedahthisabutment is separated from thelower extremity of the,

booster piston by a space sufiicientto' permit 8b the operation of thebrakes under ordinary conditions, Without bringing the booster intoact-ion. ally made so that the abutment IQ/engagcls the lower end of thebooster piston-rod 103, and the booster comes into action just beforethe master piston reaches the end of its down stroke, thereby to affordan abnormal pres,- sure in the system; or, if less of liquid hasoccurred, the booster will thereby automaticallymakc up for that loss bydrawing on the supply in the reservoir. t

In the absence of anything to prevent, it would be perfectly possiblefor the user to build up in the system an exceedingly high pressure,much greater than could be used In practice, the adjustment is usu togood advantage, and which might subject the system to unnecessary andundesirable stresses. To p event this undesirable'result,

I have provided a pressure limiting means incorporated int the link 106(see Fig. 3).

Herein, the link is telescopic, it being madeup of a rod 114 working ina sleeve 115, the latter enclosing a compression spring 116. The lowerendof this spring rests against an abutment 117 presented by the'sleeve, and at its upper-end against a nut 118 threaded onto. a rod 114.Suitable provision 1S made to permit this nut to slide longitudinally ofthe sleeve, but to be held against rotation therein, as by providingthe, nut with keyways 119 (see Fig. 3), which receive keys When, there-120 presented by the sleeve. fore, in the downward movement of the brakepedal the abutment 112 engages the booster piston rod 103, the spring116 will yield to a greater or less extent, depending upon the strength,and it will impose a limiting effect upon the action of the booster.

Adjustment of the strength of the spring can i be accomplished bydisconnecting the lower end of the link 106 from the lever 104, andturning the rod 114 in the proper direction with relation to the nut118. The rod should then be reconnected to the lever. The ascent of thesleeve relatively to the nut in opposition to the spring may be limitedby a suitable stop, herein a sleeve 121 encircling the rod 114 andresting at its lower end against the abutment 117. The length of thissleeve will be the controlling factor in determining the maximumpressure at the lowest position of the brake pedal by superscding thespring.

The details of the reservoir and the means of communication between thesame and the master cylinder will now be described, reference being badat first to Fig. 9. Near the bottom of the reservoir is a strainer 122for the operating lluid, said strainer being conveniently carried by aclean-out plug 123 threaded into the side of the reservoir. This plugcarries a sleeve 124, which is apertured as at 125 to permit theentrance of the operating liquid into its interior, and its inner end issupported in an opening 126, from which a passage 127, best shown inFig. 7, leads toward the booster cylinder, communication with the lowerend of the booster cylinder being by way of passages 128 and 129, shownin Figs. 7 and 8, with a small chamber 130, shown in Fig. 5, at thelower end of the booster cylinder. To permit the flow of the operatingliquid from the reservoir through the described passages, but to preventits flow in the reverse direction, I have provided suitable checkvalves, herein hollow pistons 131, mounted to slide in guides 132, whichpresent seats 133 for shoulders 134, which are urged toward said seats,by springs 135.

'Each valve presents a lengthwise passage 136, and one or moretransverse passages 137, the latter being directly beneath the shoulder134, whereby when the valve is lifted by the pressure of the liquid, thelatter issues fromthe transverse passages and flows between the seat andthe shoulder into a chamber 138 above the valve. Herein, the valve guide132 is threaded into the reservoir casting, and presents a shoulder 139,which rests against a gasket 140. Removal of the valve assembly isconveniently accomplished by the provision of a plug 142, threaded intothe reservoir casting, and presenting a shoulder 143 resting against agasket 144. To save space, this plug is hollow, it being provided with achamber 145,

' into which the valve assembly depends.

Referring again to Fig. 5, liquid thus drawn into the space below thebooster pis-.

' ton 102 is transferred tothe space above the latter in a manner now tobe described. In the first'place. the booster piston carries apositively opened valve 146, which is normally seated against a seat 147presented by the cylinder. This valve is opened by the upward thrust ofthe lever 104 against the booster piston rod 103. The liquid thus flowsthrough transverse passages 148 and a longitudinal passage 149 to thespace above the booster piston, the flow being controlled by aspring-seated check valve 150, which permits the flow of the liquid inan upward direction, but prevents its flow in the opposite direction. Aspring 151, interposed between a cylinder head 152 and the oosterpiston, constantly tends to urge the latter in a downward direction, andconsequently tends to cause the oil beneath the piston to flowtheretihrough to the upper side thereof, whence it flows through apassage 153 into the master cylinder 61. Preferably, the boosterpistonis provided with a cupped leather washer 154, and the. master piston issimilarly provided with a cupped leather washer 155.

In the normal operation of the brakes, the lever 104 will not reach thelower end of the booster piston rod 103. and hence the lever will simplyrise and fall idly. accompanying movement of the brake pedal. If,however, a loss of oil in the system should occur, or if. underextraordinary circumstances, the operator should wish an abnormally highpressure in the system, the pedal is depressed to an unusual extent,thereby causing the lever 104 to engage the booster piston-rod 103, thuslifting the booster piston and causing the latter to pump liquid intothe master cylinder. This operation will be repeated at each stroke ofthe pedal, if the latter, in being depressed, passes a certainpredetermined point.

\Vhcn. in the operation of the pedal, the master piston descends in itscylinder, there is a natural tendency to expel oil into the upper partof the booster cylinder, and to cause its piston to descend. \Vhen thisoccurs, its descent is limited by the valve 146 bringing up against theseat. 147, and this prevents backward flow of the liquid at this point.To prevent leakage of oil about the piston-rod 103, there is provided a.packing 156. held under compression by a gland 157,

and a sleeve 158 threaded onto the lower 1 end of the cylinder.

The connections between the master cylinder and the brake cylinders willnow be described, reference being had at first to Figs. 3 and 4. Aflexible conduit 159, helically coiled about the pivotal axis of themaster cylinder, communicates with the lower end of the latter, and isattached thereto by an appropriate coupling 160. WVhen, therefore, inthe operation of the brakes the master cylinder swings to and fro aboutits axis, communication between the master cylinder and the pipe linesis maintained by this flexible connection, which simply flexes after themanner of av helically-coiled torsional spring. This avoids thenecessity of a swivel joint at this point.

Referring now to Figs. 1 and 2, the conduit 159 is connected by ahelically-coiled,

flexible conduit 160' to a distributing valve casing 161, havingshut-off valves 162 and 163 controlling outlets leading to the front andrear axles, respectively, while another outlet is connected by a conduit164 to a pressure age 165, which in practice will )6 locate at aconvenient int for obserration by the operator, su as on the in-:trument board. Thisconduitlikewise in- :ludes a helically-coiled,flexible portion L66. This gage shows the operator the iressure in t esystem at any iven moment. The connections leading to t e front wheelrakes will now be described, reference-beng had at first to Figs. 1 and2. Leading ?rom the valve casing 1'61- is a conduit 167, which extendsalong the adjacent side memer 22 of the frame, and thence along themoss-member 23 (see Fig. 1) to a fixed itting 168. This fitting isappropriatel onnect-ed to a fittin 169 on the front ax e y a conduit,inclu ing two flexible, helially-coiled connections 170, permittinflexre about nerally horizontal parall axes nd a rigi section 171, allof which extend :ngthwise of the axle, the arrangement beag such that,as the axle and frame move p and down with relation to each. other, heseconnections bend freely and without. anger of rupture, because themovement 1euired of them is comparatively slight.

The pipe connections carried by the front x1e will now be described,reference still eing had to Fig. 13. The fitting. 169 is ttached to andcommunicates with a T-. tting 172, which in the resent example:.conveniently disposed within the hollow x1e 18. Branch ipes 173 leadin opposite irections from this T-fitting, and termiate in L-fittings174, which in turn comlunicate by way of passages 175 in the axle ad 176in the steering pivots with the brake vlinders 54. f e Theconnectionsleading to the rear brakes 'ill now be described, reference being haduce more to Figs. 1 and 2. Leadin from ievalve casin 161 is a conduit 17, inuding two hehcally-coiled, flexible sections 78 to a branch fitting179, to whose ranches are connected branch conduits 180 hich'lead'to,the rear brake cylinders 57. hese branches are conveniently supported 7diagonal'braces 181, which are attached their forward ends to the torquetube V, and diverge rearwardly toward the rear rle to which they areattached.--' .When, lerefore, the frame and rear axle move up iddownwith' relation to each other, the rnduit structures carried therebyare caable of moving with-relation to each other 7 the rovision of theflexible sections 178.

g the system with liquid, it E course 11 w to release the air thattrapped therein. In the case of .the brake dinders, this is convenientlyaccomplished y blee vents, such as yenting plugs 32 shown in Fig. 13, whle 1n the case of ie booster cylinder (see F g. ,11), there a ventinpassa 183, which leads to a. anting plug 184 ocated at a convementlyaccessible point (see the lower central portion of Fig. 4). As soon asthe liquid begins to issue from these air vents, they should be closed,and when the entire tem, including the reservoir, has been filled, thefilling cover 100 is'screwed into place. The system should then continueto oper-.- ate automatically without further attention over along periodoftime.

"The neral operation of the brake system should e evident from theforegoing, without further description,.exce t to say that the brakesare applied by epress'ing the pedal, which causes the master iston 'todescend and expel the liquid om themaster cylinder through the describedcon-' nections to the brake cylinders. When the pressure is removed fromthe brake pedal, the master piston is restored to its mitial position byits spring, while the brake levers and pistons are restored to theirinitial posi-.

tions by their respective springs. It should now be evident that thefluid system ensures equalization of action of all four brakes," thusaffording maximum braking effect while minimizing dan er of skiddingwhen the brakes are applied.

sys-

Having thus described one embodiment of the invention, but withoutlimiting-myself thereto, what I claim and desire by Letters Patent tosecure is:

1. In a fluid. brake system for vehicles, Q

the combination of abrake; two fluid motors one of which operates theother -which in turn operates said brake; one of said motors beingpivoted. to turn about an axis during its operation; and a conduitconnecting said motors. and including a flexible section coiled aboutsaid axis.

2. Ina fluid brake system for vehicles, the combination of a brake; afluid'motor which operates said brake; amaster fluid motor; a support onwhich said master fluid motor is pivoted to turn about an axis 11oduring its operation; and a conduit connecting said motors and includinga-flexlble sec-.

tion coiled adjacent said axis and partaking of the turning movement ofsaid-master fluid motor about said axis.

3. In a vehicle brake system, the combination of a brake; abrake-operatln fluid motor; a master fluid motor operated y the operatorof the vehicle for. creating a pres-' sure of the fluid in the system; anormally ino erative booster fluid motor for boosting sai pressure; andnormally ino rative means for limiting the pressure pro need by saidbooster fluid motor.

4. In a vehicle brake system, the com-,

bination of a brake; a brake-o rating fluid motor; a master fluid motorEdi creating a gressure of the fluid in the system; a booster uid motorfor boosting said pressure; an actuator for said booster fluid motor;and a connection between said actuator and said booster fluid motor tolimit the pressure produced by said booster fluid motor.

5. In a. vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor operated by theoperator of the vehicle for creating a pressure of the fluid in thesystem; a normally inoperative booster fluid motor for boosting saidpressure; and a normally inoperatlve spring for limiting the pressureproduced by said booster fluid motor.

6. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor for creating apressure of the fluid in the system; a booster fluid motor for boostingsaid pressure; an actuator for said booster fluid motor; and a springbetween said actuator and said booster fluid motor to limit the pressureproduced by said booster fluid motor.

7. In a vehicle brake system, the collibination of a brake; abrake-operating fluid motor; a master fluid motor operated by theoperator of the vehicle for creating a pressure of the fluid in thesystem; a normally inoperative booster fluid motor for boosting saipressure; and means including a normally inoperative spring forpredetermining the pressure in said system.

8. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor for creating a 1pressure of the fluid in the system; a normally inoperative boosterfluid motor for boosting said pressure; an actuator for said boosterfluid motor; and means including a spring to limit the pressure producedby said booster fluid motor during a predetermined portion of the travelof said actuator.

9. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor for creating a ressureof the fluid in the system; a booster fluid motor for boosting saidpressure; an actuator for said booster fluid motor; means including aspring to limit the pressure produced by said booster fluid motor duringa predetermined portion of the travel of said actuator; and means tosupersede said spring during the remainder of such travel and to causethe pressure to be raised above such limit.

10. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor operated by theoperator of the vehicle for creating a pressure of the fluid in thesystem; a normally inoperative booster fluid motor for boosting saidressure; a normally inoperative sprin for hmiting the pressure producedby sai booster fluid motor, and means for varying the effect oiv saidspring.

11. In a ehicle brake system, the combination a a brake; abrake-operating fluid motor; a master fluid motor for creating apressure of the fluid in the system; a booster fluid motor for boostingsaid pressure; an actuator for said booster fluid motor; a springbetween said actuator and said booster fluid motor to limit the pressureproduced by said booster fluid motor, and means for adjusting saidspring to vary its effect on said pressure.

12. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a pivoted, brake-operating master fluidmotor; a pivoted actuator for said master fluid motor; and operativeconnections between said actuator and said master fluid motor andincluding a lever compris-' ing two relatively adjustable parts to varythe normal position of said actuator with relation to said master fluidmotor.

13. In a vehicle, the combination of a brake; a brake-operating fluidmotor; a master fluid motor for actuating said brakeoperating motor; twobrackets on opposite sides, respectively, of said master motor; asupport to which one of said brackets is secured; a tie-piece connectingsaid brackets at one point; said master motor bein pivotally mounted onsaid brackets and presenting a tie-piece connecting them at anotherpoint; and a pivoted actuator connected to said master motor to actuateand to swing the same on its pivotal mounting.

14. In a vehicle, the combination of a brake; a brake-operating fluidmotor; a master fluid motor for actuating said brakeoperating motor; aunitary supporting structure comprising two brackets on opposite sides,respectively, of said master motor and on which said master motor ispivotally mounted; a master motor operating lever fulcrumed on andbetween said brackets; and a support to which one of said brackets issecured.

15. In a vehicle, the combination of a brake; a brake-operating fluidmotor; a master fluid motor for actuating said brakeoperating motor; apedal for operating said master motor; and a supporting structure forsaid. master motor and said pedal, said supporting structure having twoarts on opposite sides, respectively, of sai master motor and onopposite sides, respectively, of said pedal; said master motor beingpivoted on said parts; and a third part on which said pedal is pivoted,said third part being secured to an supported by one of said two arts.

p 16 In a vehicle, the combination of a brake; a brake-operating fluidmotor; a master fluid motor for actuating said brakeoperating motor; apedal for operating said master motor;-connections including a leverbetween said pedal and said master motor; and a supportin structure forsaid master motor, sai peda and said lever, said structure having twoparts on opposite sides.

respectively, of said master motor and on which said master motor andsaid lever are pivoted, and a third part on which said pedal is pivoted.

17. In a vehicle brake system, the combination of a brake; abrake-operatin fluid motor; a master fluid motor operated y the operatorof the vehicle for creating a pressure of fluid in the system; a boosterfluid motor for boosting said pressure; and normally inoperative meansfor imposing a limiting effect on the action of said booster Iiiotor.

18. In a vehicle brake system, the combination of a brake; abrake-operating fluid 7 motor; a master fluid motor operated by theoperator of the vehicle for creating a pres sure of fluid in the system;a booster fluid motor for boosting said ressure; and normallyinoperative means including a spring for imposing a limiting effect onthe action of said booster motor.

19. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor for creating apressure of fluid in the system; a reciproeating, booster fluid motorfor boosting said pressure; an actuator; means connecting said actuatorto said master fluid motor; and means presenting a yielding connectionbetween said actuator and said booster motor.

20. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor for creating apressure of the fluid in the system; an actuator for said master fluidmotor; a normally inoperative booster fluid motor for boosting saidpressure; and means operated by said actuator for limiting the pressureproduced by said booster fluid motor.

21. In a vehicle brake system, the combination of a brake; abrake-operating fluid motor; a master fluid motor for creating apressure of fluid in the system; a normally inoperative booster fluidmotor for boosting said pressure; and a spring for limiting the powerapplied to said booster fluid motor.-

In testimony whereof, I have signed my name to this specification.

FREDERICK. S. DUESENBERG.

